Levels are used extensively within the construction industry. They enable a determination of whether a given line or surface is horizontal or vertical when the level is positioned on the line or surface. Some levels also enable a determination of the angular inclination and/or pitch (i.e., rise and run) of a given line or surface from the horizontal or vertical.
Various types of levels are known within the industry. The most common type of level is the bubble level, also known as the “spirit level.” This type of level typically comprises an elongated body defining upper and lower longitudinal surfaces, a pair of opposing, outer ends, and has at least one liquid-filled tube or vial mounted thereon. The liquid-filled tube or vial contains a gas bubble therein while the tube or vial itself is centrally marked with one or more paired lines that define a center widow. The tube or vial is mounted to the elongated body in a generally horizontal or vertical position such that the gas bubble moves to within the center window (i.e., between the pair of lines) when the level is positioned along a respective horizontal or vertical line or surface.
For a determining whether a given line or surface is approximately horizontal (i.e., level), the liquid-filled tube is mounted to the lengthwise, elongated body, there-along or parallel therewith, such that the tube is generally horizontal and the gas bubble falls within the center window when the upper or lower edge of the body of the level is placed along a horizontal line or surface. For determining whether a given line or surface is approximately vertical (i.e., plumb), the liquid-filled tube is mounted to the lengthwise, elongated body, perpendicular thereto, such that the tube is generally horizontal and the gas bubble falls within the center window when the upper or lower edge of the body of the level is placed along a vertical line or surface. Thus, this type of level is generally limited to determining whether a given line or surface is approximately horizontal or vertical.
A variation of the bubble or spirit level has a liquid-filled tube or vial that is manually rotatable in relation to the elongated body such that the tube is generally horizontal and the gas bubble is maintained within the center window (i.e., between the paired lines) when the upper or lower longitudinal surface of the body of the level is placed along a line or surface having a predetermined angle from the vertical or horizontal. Such levels generally include markings or indicia thereon that indicate the degree of angle of inclination and/or pitch (i.e., rise and run) of such a line or surface from the horizontal or vertical when the gas bubble is within the window.
While bubble or spirit levels are simple and inexpensive, they suffer from disadvantages because their accuracy is subject to error. The position of the gas bubble within the window (i.e., between the pair of lines) is typically determined by comparing the alignment of the bubble's outer periphery with the tube's paired lines defining the window. When the upper or lower edge of the body of the level is placed along an ideally horizontal or vertical line or surface, the outer periphery of the bubble should fall equally and/or tangentially between the paired lines of the window. The accuracy errors may be attributed to the fact that a determination of the position of the bubble's periphery in relation to the paired lines of the central window is merely a visual approximation. Such an approximation may be negatively affected by physical factors, to include capillary effects existing between the liquid tube's inner surface, and temperature and pressure conditions which may cause an increase or decrease in size and/or volume of the gas bubble within the liquid.
Thus, other types of levels have been devised that do not utilize gas bubbles within liquid-filled tubes. Such levels, generally referred to as pendulum levels, accordingly utilize pendulum indicators mounted to the elongated body to determine whether a given line or surface is horizontal or vertical when an upper or lower longitudinal surface of the body of the level is placed there-along. The pendulum, comprising a weighted body suspended from a fixed point so as to swing freely under the influence of gravity, and typically including an indicator located diametrically opposite of the weighted body, generally will always maintain a vertical orientation. These pendulum levels generally include markings or indicia thereon, referenced from the vertical orientation of the pendulum, such that the degree of angle of inclination and/or pitch (i.e., rise and run) of a given line or surface from the horizontal or vertical may be readily determined.
For determining whether a given line or surface is approximately horizontal (i.e., level), the pendulum will generally be oriented perpendicular to the lengthwise, elongated body of the level when an edge of the level is placed along a horizontal line or surface. For determining whether a given line or surface is approximately vertical (i.e., plumb), the pendulum will generally be oriented parallel to the lengthwise, elongated body of the level when an edge of the level is placed along a vertical line or surface. A variation of the pendulum level includes markings or indicia thereon, referenced from the vertical orientation of the pendulum, such that the degree of angle of inclination and/or pitch (i.e., rise and run) of a given line or surface from the horizontal or vertical may be readily determined.
Like bubble or spirit levels, pendulum levels suffer from disadvantages. One such disadvantage includes a limitation of a use of the device along a single plane. Because a pendulum vertically swings from an axial pivot, movement of the pendulum is thus limited to a vertical plane of rotation about a horizontal, rotational axis. Thus, for a pendulum level to indicate whether a given line or surface is vertical or horizontal, the vertical plane of rotation of the pendulum must be maintained such that the pendulum may swing freely to its vertical, indicative orientation. Thus, where a pendulum is axially mounted to the elongated body of a level, the use of the level is limited this vertical plane or rotation. In other words, the level is rendered useless or inaccurate if it is “turned on its side” or oriented in any position outside the pendulum's vertical plane of rotation.
Another disadvantage of pendulum levels includes the fact that a swinging pendulum may oscillate (i.e., swing to and fro) before coming to rest to indicate its ultimate, vertical orientation. Although a frictional or spring-biased damper may be utilized on the axial pivot of the pendulum to minimize its oscillatory, swinging movement, such a damper may jeopardize the accuracy of the pendulum by not allowing it to reach its ultimate, vertical and indicative orientation.
Yet other types of levels have been devised with a body utilizing upwardly-facing spherical or semi-spherical liquid-filled “bulls-eye” vials having a gas bubble therein. The gas bubble, floating against the underside of the spherical or semi-spherical vial, may center itself at the intersection of two intersecting axes or windows and/or within one or more concentric circles located on the vial, thus allowing the upwardly-facing level to provide level information relative to a planar surface. However, in addition to suffering from the same disadvantages inherent in spirit levels relating to accuracy and the negative effect of physical factors, bulls-eye levels also suffer from disadvantages relating to versatility. For example, bulls-eye levels are difficult to use in relation to indicating and/or measuring level and plumb values along a single direction.